Desulfurization of phenols



/Ps/f Www/7% Nov. 11, 1952 2,617,833

V. A. KALICHEVSKY ET AL DESULFURIZATION OF PHENOLS Filed Oct. 3, 1950SHEETS-SHEET l 7 E www mf/nm/wrf/fz'1l 0 25o .5w 750 l 1000 /z50 15m1750 zum c'u/c Fff of Aw? l@ j @www Kammgfy Hans/0m' Sandhfz INVENTORSNov. 11, 1952 Filed om. 3, 195o V. A. KALICHEVSKY ET AL DESULFURIZATIONOF PHENOLS 2 SHEETS-SHEET 2 Avafous @aff/c Hyaeox/of @eff UxyaEN /7Patented Nov.`11, 1952 "KDESULFUR'IZATION 0F PHENOLS'lVlaIdimir-AKalichevsky and Hansi-ord LeeSandassignors toSocony-Vacuum" Oil Company, Incorporated, :New York, 'N.- 'Y.,- a-corporation of New York lApplication October 3, 1950,;SerialNo..188,'088

" 101'C1aims.

l-'Ihe present invention` relates7 to `the. desulfurization ofy phenolsand,-morefparticularlyftothe .desulfurization of phenols l obtainedduring the :'reningof petroleum oil,

f For= a" number` of-years thoseaskilled in the art 4, have known thatphenolic bodiesfare present in ...various fractions of petroleum oil fandy particu- 1larlyf inthe effluent vapors Ofmineral oilcrackoperations., A'particularlyrich-source of phegnnolicl bodies-is.the gasoline-obtained by crackingsuitablegcharge stock. In fact Ythe`supply "off such Y phenolic ubodies has becomev sufciently great to"have a marked .effect upon .the market -forgiphenol :andparticularlycresols. However, as recovered the phenolic "bodiesobtained` from such.; cracking-operationsare .contaminated with Isulfurv containing materials suchl as `the higher boiling :mercaptans-` ,andythiocresols from which v1 the; phenolic bodies, .predominantlyalkylphenols, ..for:.example cresols must fbe separated.

Thewpurication of petroleum alkyl -phenols :rin-the fp-astfhas beenachieved .forexample `by treatment-with aluminum; halide, zinc halide or"ferrie-halide.

It L has been Vthe practice also f to purify the ralkyl'phenolsrecovered from .petroleum rening foperations by` blowing air .through Yan aqueous alkaline isolution'of thek phenols, before liberatingthephenols by the addition `of fanacid. Thus, for example, a, typical`operation comprises passing the vapors sofY a f :gasoline fractionobtained #by catalytic cracking .fof .aiv gas oil `throughian ac lueous.alkaline sol-ut-ionof Ian alkali metal hy- .droxide Theaqueoussolutionof .alkali metal hydroxide labsorbs the .alkyl phenolstogether =with mercaptans and thiocresols. When the capabilityof `the,aqueous solutionof Aalkali vmetal 4hydroxidechas :reached ,avv.practical limit .the aqueous alkaline.v solution is said toj beAspent and ,is ready .for .treatment Tto ,recover the `dis-..solved,phenolic. bodies.

eTreatment ,of the ,spent .aqueous solution Vin-,volves.,separation-.ofsulfur compounds such as sulfhydryls, i. fr e.,..,in..'the.l form of i, alkali `metal `suliide, alkalimetal. mercaptideandalkali metal thiocresylate l from [the alkyl phenols and other.phenolic bodies. l

`One. of Y the.. most practical, j because of Asim- ,.plicity, ,methodsfor separating 'the sulfhydryls from thephenolic' bodies comprisescontacting fthe ,spent causticsolution with air under condiv'tionsWhich'lead 'tothe'formation of organic suldes from the mercaptides andthiophenelates. -This reaction can .be represented by the followingequation:

where R is an alkyl or aryl radical. .Theorganic gsuliidep-beingrelatively insoluble inthe aqueous ,alkaline f can beu separated b ygravity` and f an (Cl. i860-627) 2 aqueous alkaline solution of phenolicmaterial obt-ained .which Vhas `a satisfactory low sulfur .content.

The. phenolic bodies are recovered byaciidify- 5 ing the. disulfurizedaqueous solution bypassing flue gasL through the solution or'by adding amineral Vacid such as "hydrochloric or sulfuric acid.

The addition ofthe carbon Jdioxide of the ilue gas'orthe mineral acidreleases `the phenolic `bodies Which-riseto the top ofthe aqueoussolution and vcan-be` separated by gravity or by any other suitablemeans. The-reaction-can be represented: bythe following equation:

-It has nowbeen discoveredthatthe oxidation i offthesulfhydryls vcanAbefacceleratedby carrying out 'the oxidation fin-f the Y presence f ofIcatalytic amounts of vhypochlorites especially calcium hyypochlorite.

-It 4is lto-be..I1oted-that .petroleum distillates have.- beendesulf-urized bymeans `ofa hypochlorite in alkalinesolutionsince in1903U.-S. Patent N o. .723,368 issued for. the `desulfurization ofipetroleum vdistillates by means ofahypochlorite alkaline solution.lTreatment with sodium hypochlorite .solution is valuable primarilyforrlsweetening,straight run l or other light non-cracked petroleumproducts. (It is to.. be noted' that straight run gasolineandnon-cracked `petroleum ,products contain little, lif any, phenols.)Successful"treatmentoi any distillate with sodium hypochlorite so ,as toavoid chlorination 4`depends on 'maintaining y'within rather`narrowlimits'a -certain denitegcontent of free-alkali.'lIf-'the'-arnount of alkali` is too 10W, or especially fif itl-ie"solution `is acid, chlorination takes place. kT-he recommended range of`alkalinity of the" hypochlorite solution is usually from0.5.to Yabout3.0 .grams free Avcausticfsoda per liter :of .aqueoussolution The totalvolume of the hypochlorite: .solution used .in LtreatmentfdependsAongthe character'of :the Idistillatev and on 45 the-degree of Y refiningdesired. 'For sweetening only, the nconsumption of vhypochlorite vmayamount in terms of chlorine to only 2 to113 ypounds Vper -l-GUO gallonsofaa. gasoline; :but fornany `appreciable desulfurization 1 of the "samegasoline, 50 the consumption maybe 20,pcundsfper 1'000rgallonsvinladdition to' other: vextensive treatment.

The. hypochlorite` treatmentknown toi thepetroleum rening'industrycomprised contacting vthe .gasoline With. aqueous alkaline hypochlorite55 `solution,.for example an` aqueous-solution ofl calcium'-hypochlorite havinga free alkalinity lequivaient. tof about.. (1.3i` N,the.; treated-gasoline is separated ,from the Vfouled hypochloritesolution, WaterWashed.` and. is then` readyfor.storage-after 60 the.laddition. `of, desired. additives.

The present method of treating phenolic material distinguishes from theprior art in at least one feature; to wit; in contrast to prior arthypochlorite treatment in which ga-s containing free oxygen is not used,the present method has as its principal requirement the presence oflarge amounts of gas containing free oxygen.

The art has been taught that mercaptans can be oxidized to suldes byoxygen, i. e., air in alkaline solution in the presence of sulfides ofnickel or cobalt. Szombathy in Hungarian Patent No. 126,544 has taughtthat mercaptans and sulfhydryls in general can be oxidized in alkalinesolution with air in the presence of polyhydric phenols such ahydroquinone and pyrogallol. Bond has taught that mercaptans can beoxidized to sulfides in alkaline solutionl by air in the presence of awood tar distillate. Cauley has taught that alkyl phenols can bedesulfurized by contacting an alkaline solution of the alkyl phenolscontaining tannic acid or tannins with air. But so far as applicants areaware no one has taught that alkaline solutions of phenols can bedesulfurized by contacting with gas containing free oxygen in thepresence of catalytic amounts of a hypochlorite such as calciumhypochlorite.

The present method for producing desulfurized phenols from phenolscontaminated with sulfur compounds such as inorganic suldes andmercaptides (alkyl or aryl mercaptides) comprises dissolving phenols andcontaminating sulfur compounds in an aqueous solution of alkali metalhydroxide of such concentration that after solution of the phenols thefree alkalinity of the solution is about to about 160 grams per litercalculated as sodium hydroxide. In excess of about 0.02 weight percenthypochlorite, calculated as calcium hypochlorite and preferably about0.05 to about 1.00 weight percent hypochlorite is added to the alkalinesolution of phenols and sulfur compounds and air blown through thesolution. While the air-blowing can be at atmospheric pressure, it ispreferred to have the air or other free-oxygen containing gas under apressure of up to about 80 p. s. i. g. The temperature of blowing can beabout 100 F. to about 180 F. and preferably about 130 F. to about 160 F.

While it is preferred to use about 0.05 to about 1.00 weight percenthypochlorite calculated as calcium hypochlorite those skilled in the artwill appreciate that the upper limit is not critical and dictatedlargely by economic considerations.

It is also to be appreciated that the free alkalinity of the solution isimportant to prevent chlorination of the product. However, the lower thealkalinity the more effective is the effect of the hypochlorite as anoxidation promoter.

Illustrative of the application of the present method to the productionof desulfurizecl phenols, especially alkyl phenols, from petroleum isthe following.

The vapors from a catalytic cracking wherein a suitable gas oil iscracked over a silica-alumina catalyst were condensed and the condensatecontacted with an aqueous solution of alkali metal hydroxide. When thecapability of the aqueous solution for absorbing alkyl phenols andsulfur compounds had been reduced to a practical minimum, 0.05 weightpercent calcium hypochlorite was added and the spent solution blown withair at about 150 F.' until the sulfur content was reduced to asatisfactory minimum. The sulfur compounds produced during theair-blowing rose to the top of the aqueous solutQQ WJQD, ul@ @t/? 4 wasquiescent and were readily separated therefrom.

The desulfurized aqueous solution was then treated with suflicient acidto set free the phenols which rose to the top when the mixture wasquiescent and were readily removed.

Thus, a hydrocarbon fraction containing alkyl phenols and mercaptans canbe treated to obtain substantially pure alkyl phenols in a mannerdiagrammatically represented by the iiow sheet Figure 2. Aqueous caustichydroxide having a gravity of about 10 to about 35 B. is introduced intocontainer I0 through line II. Container I0 is of suitable type in whichan intimate contact between two substantially immiscible liquids can beobtained. A petroleum fraction containing alkyl phenols (AROH) andaliphatic and/or aromatic sulfhydryls (RSI-l) is introduced through lineI2 into container I0. The petroleum fraction rises through the aqueousalkaline solution and during its i'low upward through container I0 isstripped, at least in part, of its phe-r nols and sulfhydryls by theaqueous caustic solution. The treated petroleum fraction leavescontainer I0 through line I3. The aqueous caustic solution with thephenols and mercaptans stripped from the petroleum leaves container I0through line I4. A metal hypochlorite such as calcium hypochlorite isintroduced into the aqueous caustic hydroxide solution containingphenols and sulfhydryls in line I4 through line I5 in catalytic amountsto provide a concentration of at least 0.02 weight per cent hypochloritecalculated as calcium hypochlorite. The aqueous caustic hydroxidesolution containing phenols, sulfhydryls and hypochlorite flows throughline Ill to container I6 which is of any suitable type in which contactcould be made between a gas and the aqueous caustic solution. A gascontaining free oxygen is introduced through line I1 into container IB.The gas flows upwardly through the aqueous caustic solution and inpassage therethrough oxidizes the mercaptans to polysuldes, (RSSB.) thegas escaping from container I6 through line 24. After the sulfhydryls'have been converted to polysulfldes, the polysuldes rise to the top ofthe aqueous solution and are drawn off through line I8. The aqueouscaustic solution substantially devoid of sulfhydryls containing thephenols is withdrawn from container I6 through line I9 to vat 20. In vat20 suicient reagent such as sulfuric acid or acidic gas such as ue gasis introduced through line 2| in amounts suicient to spring or releasethe phenols from the caustic solution. The phenols riseto the top of theaqueous solution and are drawn olf through line 22, the aqueous solutionof the salts of the alkali metal hydroxide is withdrawn from vat 20through line 23. Since substantially all of the sulfhydryls have beenseparated from the aqueous caustic solution in container I6, it followsthat the phenols sprung in vat 20 are substantially devoid ofsulfhydryls.

Suitable starting solutions are aqueous solutions of sodium hydroxidehaving a gravity of 10 to about 35 B., aqueous solutions of potassiumhydroxide having a gravity of about 10 to about B.

Spent aqueous solutions of phenols and contaminating sulfur compoundshave a gravity of about 7 to about 30 B. and a free alkalinity of about0 to about 160 grams per liter (0 to about 1.3 pounds per gallon).

One virtue of the present method of desulfilming Phengl'il ,alkalinesolution in the pres- "ence 'of' :catalytic-amounts A'of hypochlcritelisffthe marked' reduction'` in' theyolume of^oxygencon taining gas"`required' to desulfurize the phenols.

` Thevolume'nfv air, forexample,frequired to desulfurizeasolution of;given 'sulfur content is reducedas"1muchas65% by 'theuse of catalyticamounts of hypochlorite. This is manifest from a comparison'ofy theamount of air required to reduce the RSH content of an alkaline solutionof "phenolsfrom 0.75 Weight-percent toa'given mercaptide concentration.

Seven liters of -spent caustic solution Were blown with air at 15 p. s.i. g. and 150 F. Seven liters vofj'the'A same spent caustic'solutionWere yblovvn With airv at 15` p. s. i; g. and'150" F. after the additionof 0.05 Weight percent calcium hypochlorite. The sulfur content wasreduced as shown by the data in Tables I and II:

TABLE I (No hypochlorite) Air ft NagS, Wt. RSH, Wt. Gravity,

Percent Percent Ba 60 F.

037 0. 75 20. 5 None 0. 54 20. 4 None 0.38 20. 4 None 0.165 20. 5 None0.071 20. 5

TABLE II (0.05 wt. percent Ca hypochlorzte) NaiS, Wt. RSH, Wt. All" maPercent Percent 0. 037 0. 75 None 0. 055 None 0. 029 None 0. 0ll

The values for Weight percent RSH given in Tables I and II were plottedas in the accompanying drawing; the circles being used for the data ofTable I and the squares for the data of Table II. From the curves soobtained the amount of air required to reduce the RSH content to 0.6,0.5 etc. Weight percent was estimated for the desulfurization in theabsence of added catalyst and for desulfurization in the presence ofadded hy- We claim:

1. A method of desulfurizing phenols contaminated with mercaptans whichcomprises oxidizing said mercaptans in alkaline solution in the presenceof a catalytic amount of a hypochlorite.

2. A method of desulfurizing phenols contaminated with mercaptans whichcomprises contacting an aqueous alkaline solution containing phenols andmercaptans with gas containing free oxygen in the presence of acatalytic amount of calcium hypochlorite.

3.Y VA method Vof 1 desulfurizing phenols which -w4.-'-A methodfdesulf-urizing-phenolslwhich 'comprises contactingA an i aqueousfalkaline rrsolu- Ationa containing-'phenols and Ymercaptansr with `gascontaining freeoxygen inthe presence of a "catalyticamountof calciumhypochlorite.`

"55.L A method of desulfurizing phenols `which comprisesv` contactingan` aqueous f-alkaline solu- `tion 'containing phenols and Y mercaptans`with airl inthe presence 'of-about 0.05'vveight percent calciumhypochlorite.

6. A method for producing desulfurized phenols from petroleum fractionswhich comprises contacting a petroleum fraction containing phenols andmercaptans with an aqueous solution of alkali metal hydroxide to obtaina fat solution containing alkali metal hydroxide, phenols andmercaptans, separating said fat solution from said treated fraction,adding a catalytic amount of a hypochlorite to said fat solution,contacting said fat solution containing hypochlorite with gas containingfree oxygen to convert said mercaptans into sulfur containing compoundssubstantially insoluble in said aqueous solution, separating saidsubstantially insoluble sulfur compounds from the aqueous solution,acidifying said aqueous solution to produce free phenols and separatingsaid free phenols.

7. A method for producing desulfurized phenols from petroleum fractionswhich comprises contacting a petroleum fraction containing phenols andmercaptans with an aqueous solution of alkali metal hydroxide to obtaina fat solution containing alkali metal hydroxide, phenols andmercaptans, separating said fat solution from said treated fraction,adding a catalytic amount of calcium hypochlorite to said fat solution,contacting said fat solution containing hypochlorite with gas containingfree oxygen to convert said mercaptans into sulfur containing compoundssubstantially insoluble in said aqueous solution, separating saidsubstantially insoluble sulfur compounds from the aqueous solution,acidifying said aqueous solution to produce free phenols and separatingsaid free phenols.

8. A method for producing desulfurized phenols from petroleum fractionswhich comprises contacting a petroleum fraction containing phenols andmercaptans With an aqueous solution of alkali metal hydroxide to obtaina fat solution containing alkali metal hydroxide, phenols andmercaptans, separating said fat solution from said treated fraction,adding about 0.05 weight percent of calcium hypochlorite to said fatsolution, contacting said fat solution containing hypochlorite with gascontaining free oxygen to convert said mercaptans into sulfur containingcompounds substantially insoluble in said aqueous solution, separatingsaid substantially insoluble sulfur compounds from the aqueous solution,acidifying said aqueous solution to produce free phenols and separatingsaid free phenols.

9. In the process of desulfurizing phenols which comprises contacting anaqueous alkaline solution containing phenols and mercaptans with airuntil the mercaptan-sulfur content thereof is reduced to a given valueand separating the polysuldes thereby formed from said aqueous alkalinesolution, the improvement which comprises adding not lmore thany acatalytic amount of a hypochlorite to said aqueous solution beforecontacting With air and then contacting said aqueous alkaline solutionwith not more than about 0.6 as much air as required in the absence ofsaid catalytic amount of hypochlorite to reduce the mercaptan-sulfur ofsaid aqueous solution to said given value.

10. A method of desulfurizing phenols which comprises contactingY anaqueous solution containing phenols, mercaptans and about 0.02 toabout 1. Weight per cent of hypochlorite and having a free alkalinity ofup to about 160 grams per liter calculated as sodium hydroxide with 152,134,390

`V8 gas containing free oxygen until the mercaptansulfur content hasbeen reduced to a given value and polysuldes are formed, and separatingsaid polysuldes from said aqueous alkaline solution.

VLADIMIR A. KALICHEVSKY. HANSFORD LEE SANDLIN.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Name Date Greensield-er et ai. Oct. 25, 1938Number

6. A METHOD OF PRODUCING DESULFURIZED PHENOLS FROM PETROLEUM FRACTIONSWHICH COMPRISES CONTACTING A PETROLEUM FRACTION CONTAINING PHENOLS ANDMERCAPTANS WITH AN AQUEOUS SOLUTION OF ALKALI METAL HYDROXIDE TO OBTAINA FAT SOLUTION CONTAINING ALKALI METAL HYDROXIDE, PHENOLS ANDMERCAPATANS, SEPARATING SAID FAT SOLUTION FROM SAID TREATED FRACTION,ADDING A CATALYTIC AMOUNT OF A HYPOCHLORITE TO SAID FAT SOLUTION,CONTACTING SAID FAT SOLUTION CONTAINING HYPOCHLORITE WITH GAS CONTAININGFREE OXYGEN TO CONVERT SAID MERCAPTANS INTO SULFUR CONTAINING COMPOUNDSSUB-